This invention relates to an electroless copper plating solution, and particularly to an electroless copper plating solution which can give an electroless plated copper film with high strength.
In order to give electroless plated copper films with high strength, there is proposed an electroless copper plating solution comprising copper(II) ions, a reducing agent for copper(II) ions, a complexing agent for copper(II) ions, a pH adjustor, .alpha.,.alpha.'-dipyridyl, polyethylene glycol, and an alkali-soluble inorganic silicon compound (Japanese Patent Appln Kokai (Laid-Open) No. 19430/79).
But this electroless copper plating solution uses polyethylene glycol as surface active agent and contains the alkali-soluble inorganic silicon compound in an amount of as low as 5 to 100 mg/l in terms of SiO.sub.2 (0.08 to 1.7 mmole/l in terms of Si atom), so that the resulting electroless plated copper film is improved in tensile strength and elongation but the stability of the plating solution is not good and there takes place abnormal deposition (a phenomenon of depositing copper on outside of desired portions) when the plating solution is used continuously for a little prolonged time.